In an environment in which national polling has been all but impossible, insurgent attacks on polling places are likely to deter turnout, and money to buy votes is at least as important as the political promises of the candidates, the election is impossible to call.
Numerous high-profile attacks just ahead of Saturday's vote – including on a heavily fortified hotel and Afghanistan's election headquarters – underscore how hard it is to get to "free" and "fair" in Afghan elections.
But it does seem clear that one of four men will lead Afghanistan after Mr. Karzai.
Mr. Rassoul served as Karzai's foreign minister for three years until stepping down to run for president last October. He is Karzai's favored candidate. His ticket includes a notable first for Afghanistan: his female vice-presidential running mate, Habiba Sarobi.
Rassoul doesn't have much of a power base of his own and how much Karzai's patronage network will help him is an open question. While the president has amassed a lot of power in 12 years, he is now a lame duck, and his ability to keep promises and extract favors from other prominent Afghans is on the wane.
Ashraf Ghani Ahmadzai
Mr. Ghani is probably the American preference to lead Afghanistan.
He lived in exile from the late-1970s until the fall of the Taliban, worked at the World Bank for a decade, and was an adviser to the Bonn, Germany, conference that brought Karzai to power with the blessings of NATO and the United States. He served for a time in Karzai's government as finance minister, and mounted a failed challenge for the presidency in 2009, garnering less than 5 percent of the vote.
Like Rassoul, he has a limited power base. But he does have a powerful ally in his running mate, Rashid Dostum, the ethnic Uzbek warlord whose support for Karzai in 2009 helped swing the election for him.
Another former foreign minister, Mr. Abdullah has become a vocal critic of corruption under Karzai.
He dropped out of the runoff in the 2009 election complaining of vote-rigging. He was close to Ahmad Shah Massoud, the Northern Alliance commander who was assassinated in 2001, and has meaningful support among the nation's ethnic Tajiks.
Will that be enough to win (and hold) power?
That is hard to say. Abdullah has been a staunch opponent of the Taliban, but has also spoken at times of a willingness to conclude peace talks with the Taliban.
Abdul Rassoul Sayyaf
An ethnic Pashtun, Mr. Sayyaf is the sort of man the US probably doesn't want leading Afghanistan. A fearsome military commander in the war against the Soviet Union and in the Afghan civil war in the 1990s, he's an opponent of the Taliban – but he also had warm relations with Osama bin Laden when Mr. bin Laden moved to Afghanistan in the mid-1990s.
He's also a current member of parliament and a preacher, but his mujahideen roots are still visible. When he announced his candidacy last October, he paraded through Kabul with gun-toting loyalists.